High quality Bluetooth audio earphones conform to the Advanced Audio Distribution Profile (A2DP). Currently, so-called Bluetooth “Wireless” headsets use a wireless connection to transfer stereo audio signals between the audio source and a first one of two earphones. The first earphone contains a wireless receiver. One of the audio channels is played in the first earphone, and the other audio channel is provided to the second earphone by way of a wired link. This increases the physical size of the earphone set and makes the earphones more conspicuous and difficult to use. Also, their large size makes them inconvenient to carry. A typical stereo Bluetooth earphone set is much larger than a typical flash or hard disk based music player, such as an “IPOD”® (sold by Apple, Inc. of Cupertino, Calif.).
Bluetooth A2DP signal sources can theoretically support up to seven earphones—the protocol allows a single Bluetooth master to interleave traffic between up to seven simultaneously active slaves in a single piconet. (A Bluetooth piconet is a temporary wireless network formed between Bluetooth devices. Devices participating in a Bluetooth piconet use the same frequency hop spread spectrum (FHSS) sequence.) In practice, however, the maximum number of A2DP links is fewer than seven, because of the lack of bandwidth inside a single Bluetooth piconet. It is common to aggregate up to five of the available time slots for a transmission to a single slave, reducing the amount of bandwidth available for the rest of the slaves. The inventor is not aware of any commercially available A2DP source that can transmit signals to more than one A2DP earphone at a time.
Improved Bluetooth earphones are desired.